
Two-sample t test with equal variances
------------------------------------------------------------------------------
   Group |     Obs        Mean    Std. Err.   Std. Dev.   [95% Conf. Interval]
---------+--------------------------------------------------------------------
 control |  17,281    21835.68    173.3202    22784.19    21495.96    22175.41
experime |  17,281    21812.56    172.9356    22733.63    21473.59    22151.53
---------+--------------------------------------------------------------------
combined |  34,562    21824.12    122.4182     22758.6    21584.18    22064.06
---------+--------------------------------------------------------------------
    diff |            23.11923      244.84               -456.7751    503.0136
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    diff = mean(control) - mean(experime)                         t =   0.0944
Ho: diff = 0                                     degrees of freedom =    34560

    Ha: diff < 0                 Ha: diff != 0                 Ha: diff > 0
 Pr(T < t) = 0.5376         Pr(|T| > |t|) = 0.9248          Pr(T > t) = 0.4 624
